File: gawk.info,  Node: Calling A Function,  Next: Variable Scope,  Up: Function Calling

9.2.3.1 Writing a Function Call
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A function call consists of the function name followed by the arguments
in parentheses.  'awk' expressions are what you write in the call for
the arguments.  Each time the call is executed, these expressions are
evaluated, and the values become the actual arguments.  For example,
here is a call to 'foo()' with three arguments (the first being a string
concatenation):

     foo(x y, "lose", 4 * z)

     CAUTION: Whitespace characters (spaces and TABs) are not allowed
     between the function name and the opening parenthesis of the
     argument list.  If you write whitespace by mistake, 'awk' might
     think that you mean to concatenate a variable with an expression in
     parentheses.  However, it notices that you used a function name and
     not a variable name, and reports an error.